TW201631257A - Engine, cylinder body member, and vehicle - Google Patents

Abstract

The present invention addresses the problem of providing an engine capable of more effectively inhibiting the formation of scuffs in the vicinity of top dead centre. This engine is provided with a piston part, and a cylinder body part having a sliding surface along which the piston part slides. The engine is characterized in that: the cylinder body part is formed from an Al alloy having an Si content of at least 16 mass%, and includes primary Si crystal grains having an average crystal grain size of 8-50 [mu]m inclusive, eutectic Si crystal grains having an average crystal grain size smaller than that of the primary Si crystal grains, and an Al alloy base material; and, in the sliding surface, in an area comprising at least 1/4 of the upper side of the sliding surface, the primary Si crystal grains and the Al alloy base material are exposed so as to come into contact with the piston part, and a plurality of substantially parallel linear grooves, which have a depth of at least 1/3 of the upper limit value of the range of the eutectic Si crystal grain sizes in the grain size distribution of the Si crystal grains in the cylinder body part, are formed at a pitch greater than the average crystal grain size of the primary Si crystal grains, and have sections which pass between adjacent primary Si crystal grains.

Description

Engine, cylinder block components and vehicles

The present invention relates to an engine, a cylinder block member, and a vehicle.

In recent years, in order to reduce the weight of the engine, Al alloying of the cylinder block portion has been promoted. High strength and high wear resistance are required for the cylinder body. Therefore, one of the Al alloys for the cylinder block portion is an Al-Si alloy containing a large Si alloy, that is, a hypereutectic composition.

Patent Document 1 relates to an engine having a cylinder made of an Al alloy having a relatively high Si content, and discloses the following technique.

On the sliding surface of the cylinder block and the piston ring, Si crystal grains and an Al alloy base material are exposed. The sliding surface is mechanically machined in such a manner that the Si grains float. The exposed surface of the Si crystal grains is located on the inner side of the cylinder than the exposed surface of the Al alloy base material. Therefore, the piston ring is in contact with the Si crystal grains. The piston ring can be prevented from coming into contact with the Al alloy base material. Further, the cylinder body contains an Al alloy having a relatively high Si content and is produced by high pressure die casting. Therefore, the primary Si crystal grains having an appropriate size are appropriately distributed on the sliding surface. When the engine is operated, the load applied to each of the primary Si crystal grains is reduced, so that the destruction of the primary Si crystal grains can be suppressed. Further, since the primary Si crystal grains have an appropriate size, it is possible to suppress the primary Si crystal grains from falling off from the sliding surface. Thereby, the piston ring can be effectively prevented from coming into contact with the Al alloy base material. Therefore, the occurrence of the drag caused by the contact of the Al alloy base material with the piston ring can be suppressed. Further, lubricating oil is held between the Si crystal grains floating to the sliding surface, and the recess between the Si crystal grains functions as an oil reservoir. Thereby, the lubricity of the piston when sliding in the cylinder is improved, and the drag resistance of the cylinder block portion is improved.

As described above, in the cylinder of Patent Document 1, the primary Si crystal grains having an appropriate size are exposed in a floating island shape so that the sliding surfaces are distributed at an appropriate density. Thereby, the Al alloy base material can be prevented from coming into contact with the piston ring, and the recess between the Si crystal grains functions as an oil reservoir. As a result, the occurrence of dragging can be suppressed.

Patent Literatures 2 and 3 are similar to Patent Document 1, and relate to an engine having a cylinder made of an Al alloy having a relatively high Si content.

In the cylinder of Patent Document 2, the sliding surface is etched so that the Si crystal grains float. Concavities and convexities are formed on the surface of the Al alloy base material located in the recess between the Si crystal grains by etching. As a result, the amount of the lubricating oil held by the recess between the Si crystal grains is larger than that of the patent document 1. Therefore, the occurrence of the drag can be more effectively suppressed.

In the cylinder of Patent Document 3, the sliding surface is etched so that the unevenness formed on the surface of the Al alloy base material located in the recess between the Si crystal grains near the top dead center becomes deeper. As a result, the amount of lubricating oil held by the recess between the Si grains located near the top dead center increases. It can more effectively suppress the occurrence of the drag near the top dead center.

Near the top dead center, the lubrication of the sliding surface and the piston portion is mainly boundary lubrication. Again, the top dead center is close to the combustion chamber of the engine. Therefore, the lubrication conditions near the top dead center are stricter. Dragging is easy to produce near the top dead center. Therefore, as in Patent Document 3, a technique for suppressing the drag around the top dead center has been proposed.

As described above, in the case where the Si crystal grains are exposed in a floating island shape, the cylinder of the Al alloy manufactured by high-pressure die casting is upgraded with a relatively high Si content. In other words, the basis of the technical flow of the cylinder made of Al alloy which is relatively high in Si content and manufactured by high pressure die casting has the premise that the drag can be suppressed by implementing the following two aspects: suppressing the piston ring and the Al alloy mother The contact of the material; and the recess between the Si crystal grains functions as an oil reservoir.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2005-273654

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2008-180218

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2010-31840

The present invention provides an engine, a cylinder block member, and a vehicle that can more effectively suppress the occurrence of drag around the top dead center.

The present invention can adopt the following constitution.

(1) An engine comprising: a piston portion; and a cylinder block portion having a sliding surface on which the piston portion slides, wherein the cylinder block portion is formed of an Al alloy having a Si content of 16% by mass or more, and includes an average a primary crystal Si crystal grain having a crystal grain size of 8 μm or more and 50 μm or less, a eutectic Si crystal grain having an average crystal grain size smaller than an average crystal grain size of the primary Si crystal grain, and an Al alloy base material, a region of at least 1/4 of an upper side of the sliding surface of the sliding surface, wherein the primary Si crystal grain and the Al alloy base material are exposed in contact with the piston portion, and have a grain size of the Si crystal grain of the cylinder body portion a substantially parallel plurality of linear grooves having a depth equal to or more than 1/3 of the upper limit of the range of the eutectic Si crystal grain size in the distribution, which is wider than the average crystal grain size of the primary Si grains Formed and has a portion passing between the adjacent primary Si grains.

In the configuration of (1), the cylinder block portion is formed of an Al alloy having a Si content of 16% by mass or more. The average crystal grain size of the primary Si crystal grains exposed in the region of 1/4 of the upper side of the sliding surface is 8 μm or more and 50 μm or less. From the viewpoint of bearing the load of the piston portion, the primary Si crystal grains have an appropriate size and are appropriately distributed on the sliding surface. Under this condition, the primary Si crystal grains and the Al alloy base material are exposed in contact with the piston portion, and have the above-described cylinder body portion. a substantially parallel plurality of linear grooves having a depth equal to or more than 1/3 of the upper limit of the range of the eutectic Si crystal grain size in the particle size distribution of the Si crystal grains, which is wider than the average crystal of the primary Si crystal grains The distance between the particle diameters is formed. The substantially parallel plurality of linear grooves are formed to be wider than the average crystal grain size of the primary Si crystal grains, whereby the uniformity of dispersion of the lubricating oil on the sliding surface can be improved. Thereby, the uniformity of the oil film formed on the sliding surface can be improved. Further, the plurality of linear grooves have a depth of 1/3 or more of the upper limit of the range of the eutectic Si crystal grain size in the particle size distribution of the Si crystal grains of the cylinder block portion, so that a sufficient amount of lubrication can be provided. The oil remains in the tank. Therefore, the oil film crack on the sliding surface can be suppressed. Further, a plurality of linear grooves have portions passing between adjacent primary Si crystal grains. As a result, since the primary Si crystal grains are subjected to the load of the piston portion, abrasion of the sliding surface (Al alloy base material) adjacent to both sides of the groove can be suppressed, and the lubricating oil in the groove can be easily held.

The Al alloy base material is exposed to the sliding surface so as to be in contact with the piston portion. Previously, it has been considered that the contact between the Al alloy base material and the piston portion is poor in terms of suppressing the drag. However, in the configuration of (1), the Al alloy base material is exposed to the sliding surface together with the primary Si crystal grains having an appropriate size and appropriately distributed on the sliding surface. Further, as described above, in the configuration of (1), the uniformity of the oil film formed on the sliding surface can be improved, and a sufficient amount of lubricating oil can be maintained. Therefore, the influence of the contact between the Al alloy base material and the piston portion can be suppressed to an allowable degree, and the effect of suppressing the drag by the improvement of the uniformity of the oil film can be obtained. As a result, the occurrence of the drag can be more effectively suppressed.

(2) An engine comprising: a piston portion; and a cylinder body portion having a sliding surface on which the piston portion slides, wherein the cylinder block portion is an Al alloy having a Si content of 16% by mass or more by high pressure die casting. a eutectic Si crystal grain having a primary crystal Si grain, an average crystal grain size smaller than an average crystal grain size of the primary crystal Si grain, and an Al alloy base material, and at least the above-mentioned sliding surface a region of 1/4 of the upper side of the sliding surface, wherein the primary Si crystal grains and the Al alloy base material are exposed in contact with the piston portion, and have a substantially parallel plurality of linear grooves having a depth equal to or more than 1/3 of a range of the upper limit of the range of the eutectic Si crystal grain size in the particle size distribution of the Si crystal grains of the cylinder block portion, which is wider than the primary crystal The average crystal grain size of the Si crystal grains is formed at a distance therebetween, and has a portion passing between the adjacent primary Si crystal grains.

According to the configuration of (2), the cylinder block portion is formed of an Al alloy having a Si content of 16% by mass or more by high pressure die casting. From the viewpoint of bearing the load of the piston portion, the primary Si crystal grains have an appropriate size and are appropriately distributed on the sliding surface. Under this condition, the primary Si crystal grains and the Al alloy base material are exposed in contact with the piston portion, and have a range of the eutectic Si crystal grain size in the particle size distribution of the Si crystal grains of the cylinder block portion. The substantially parallel plurality of linear grooves having a depth of 1/3 or more of the upper limit are formed to be wider than the average crystal grain size of the primary Si grains. The substantially parallel plurality of linear grooves are formed to be wider than the average crystal grain size of the primary Si crystal grains, whereby the uniformity of dispersion of the lubricating oil on the sliding surface can be improved. Thereby, the uniformity of the oil film formed on the sliding surface can be improved. Further, the plurality of linear grooves have a depth of 1/3 or more of the upper limit of the range of the eutectic Si crystal grain size in the particle size distribution of the Si crystal grains of the cylinder block portion, so that a sufficient amount of lubrication can be provided. The oil remains in the tank. Therefore, the oil film crack on the sliding surface can be suppressed. Further, a plurality of linear grooves have portions passing between adjacent primary Si crystal grains. As a result, since the primary Si crystal grains are subjected to the load of the piston portion, abrasion of the sliding surface (Al alloy base material) adjacent to both sides of the groove can be suppressed, and the lubricating oil in the groove can be easily held.

The Al alloy base material is exposed to the sliding surface so as to be in contact with the piston portion. Previously, it has been considered that the contact between the Al alloy base material and the piston portion is poor in terms of suppressing the drag. However, in the configuration of (2), the Al alloy base material is exposed to the sliding surface together with the primary Si crystal grains having an appropriate size and appropriately distributed on the sliding surface. Further, as described above, in the configuration of (2), the uniformity of the oil film formed on the sliding surface can be improved, and a sufficient amount of lubricating oil can be maintained. Therefore, the influence of the contact between the Al alloy base material and the piston portion can be suppressed to an allowable degree, and the effect of suppressing the drag by the improvement of the uniformity of the oil film can be obtained. fruit. As a result, the occurrence of the drag can be more effectively suppressed.

(3) The engine of (1) or (2), wherein the plurality of linear grooves have an upper limit value of a range of the eutectic Si crystal grain size in a particle size distribution of Si crystal grains of the cylinder block portion One third or more and less than the depth of the upper limit of the range of the eutectic Si crystal grain size.

According to the constitution of (3), a sufficient and appropriate amount of lubricating oil can be held in a plurality of linear grooves. Therefore, the effect of the drag suppression by the improvement of the uniformity of the oil film can be improved. As a result, the occurrence of the drag can be effectively suppressed.

(4) The engine according to any one of (1) to (3) wherein the plurality of linear grooves have a depth of 2.0 μm or more and 6.0 μm or less.

According to the constitution of (4), a sufficient and appropriate amount of lubricating oil can be held in a plurality of linear grooves. Therefore, the effect of the drag suppression by the improvement of the uniformity of the oil film can be improved. As a result, the occurrence of the drag can be effectively suppressed.

(5) The engine of any one of (1) to (4), wherein between the adjacent linear grooves, the primary Si crystal grains and the Al alloy base material are combined with the above The piston portion is exposed to the sliding surface.

According to the configuration of (5), the Al alloy base material is interposed between the adjacent linear grooves, and is exposed to the sliding surface together with the primary Si crystal grains in contact with the piston portion. Therefore, the abrasion of the sliding surface (Al alloy base material) can be more effectively suppressed. It is easier to keep the lubricant in the tank. Therefore, the occurrence of the drag can be effectively suppressed.

(6) The engine of any one of (1) to (5), wherein the piston portion includes: a piston body; and a piston ring portion including a plurality of piston rings disposed on an outer circumference of the piston body; The linear groove is formed by a pitch wider than an average crystal grain size of the primary Si crystal grains and smaller than a distance from a lower end of the piston ring portion to an upper end of the piston ring portion in a reciprocating direction of the piston portion. .

According to the configuration of (6), a sufficient and appropriate amount of lubricating oil can be held in a plurality of linear grooves. Therefore, the effect of the drag suppression by the improvement of the uniformity of the oil film can be improved. As a result, the occurrence of the drag can be effectively suppressed.

(7) The engine of any one of (1) to (6), wherein the piston portion is provided with: a piston body; and a piston ring disposed at an outer circumference of the piston body; the plurality of linear grooves having a smaller diameter than The width of the thickness of the piston ring.

According to the configuration of (7), it is possible to suppress the piston ring from entering or being caught in the groove when the piston ring slides on the sliding surface. As a result, the reciprocating movement of the piston portion can be performed more smoothly, so that the occurrence of the drag can be effectively suppressed.

(8) The engine according to any one of (1) to (7), wherein at least a part of the primary Si crystal grains exposed on the sliding surface is broken, and the surface of the primary Si crystal is exposed due to being broken. On the above sliding surface.

According to the configuration of (8), the surface formed on the primary Si crystal grains (hereinafter also referred to as a broken cross section) due to being broken functions as an oil reservoir. The fracture surface of the primary Si crystal has irregularities, so that the amount of lubricating oil that can be maintained in the oil reservoir is large. The opening area of the oil reservoir is, for example, the same as the sectional area of the primary Si crystal grains. The depth of the oil reservoir is, for example, smaller than the diameter of the primary Si crystal grains. In this manner, the oil reservoir portion including the fractured portion of the primary Si crystal grains is formed on the sliding surface together with a plurality of substantially linear grooves. Therefore, the amount of the lubricating oil can be increased while maintaining the uniformity of the dispersion of the lubricating oil. It can suppress the grinding more effectively.

(9) A cylinder block member comprising the cylinder block portion included in the engine of any one of (1) to (8).

According to the configuration of (9), it is possible to provide a cylinder block member which can more effectively suppress the occurrence of the drag near the top dead center.

(10) A vehicle comprising the engine of any one of (1) to (8).

According to the configuration of (10), it is possible to provide a vehicle having an engine that can more effectively suppress the occurrence of drag around the top dead center.

According to the present invention, the occurrence of the drag near the top dead center can be more effectively suppressed.

1‧‧‧ primary crystal Si grain

2‧‧‧ Eutectic Si grains

3‧‧‧Al alloy base metal

5a‧‧‧ broken section

5b‧‧‧Oil Accumulation Department

8‧‧‧Line slot

8a‧‧‧First linear groove

8b‧‧‧second linear groove

100‧‧‧Cylinder body (cylinder block)

101‧‧‧Sliding surface

101a‧‧‧1⁄4 area above the sliding surface

101b‧‧‧1⁄4 area below the sliding surface

102‧‧‧Cylinder bore

103‧‧‧ cylinder wall

104‧‧‧ outer wall

105‧‧‧ water jacket

110‧‧‧ crankcase

111‧‧‧ crankshaft

112‧‧‧ crank pin

113‧‧‧ crank arm

114‧‧‧Roller bearings (rolling bearings)

122‧‧‧Piston Department

122a‧‧‧Piston body

122b‧‧‧Piston ring

122c‧‧‧Top ring (piston ring)

122d‧‧‧Second ring (piston ring)

122e‧‧‧ Oil ring (piston ring)

122f‧‧‧Top ring groove

122g‧‧‧second ring groove

122h‧‧‧ Oil ring groove

Upper end of 122m‧‧‧ (of piston ring 122b)

122n‧‧‧ (lower piston ring portion 122b) lower end

123‧‧‧Piston pin

130‧‧‧Cylinder head

131‧‧‧ combustion chamber

132‧‧‧Intake 埠

133‧‧‧Exhaust gas

134‧‧‧Intake valve

135‧‧‧Exhaust valve

140‧‧‧ Connecting rod

142‧‧‧ small end

144‧‧‧ big end

150‧‧‧ engine

301‧‧‧ ontology framework

302‧‧‧ head tube

303‧‧‧ Front fork

304‧‧‧ front wheel

305‧‧‧Handle

306‧‧‧post frame

307‧‧‧fuel tank

308a‧‧‧Main seat

308b‧‧‧ rear seat

309‧‧‧ rear arm

310‧‧‧ Rear wheel

311‧‧‧ radiator

312‧‧‧Exhaust pipe

313‧‧‧Muffler

315‧‧ ‧transmission machine

316‧‧‧ Output shaft

317‧‧‧Drive sprocket

318‧‧‧Chain

319‧‧‧ Rear wheel sprocket

L‧‧‧down direction

R‧‧‧Reciprocating direction of the piston

U‧‧‧Up direction

Fig. 1 is a cross-sectional view schematically showing an engine 150 according to an embodiment of the present invention.

Fig. 2 is a side view schematically showing the piston portion 122 of the engine 150 shown in Fig. 1.

FIG. 3 is a perspective view schematically showing a cylinder block 100 provided in the engine 150 shown in FIG. 1 .

Fig. 4 is a cross-sectional view schematically showing the cylinder block portion 100 shown in Fig. 3.

Fig. 5 is a partially enlarged plan view schematically showing the sliding surface 101 of the cylinder block 100 shown in Fig. 3.

6(a) and 6(b) are partially enlarged cross-sectional views schematically showing the sliding surface 101 of the cylinder block 100 shown in Fig. 3.

Fig. 7 is a graph showing an example of a preferable particle size distribution of Si crystal grains.

Fig. 8 is a side view schematically showing a locomotive having the engine 150 shown in Fig. 1.

Conventionally, in a cylinder block made of an Al alloy which is made of a high Si content and which is produced by high pressure die casting, the sliding surface is processed so that the primary Si crystal grains are exposed in a floating island shape. In the sliding surface, the contact between the piston ring and the Al alloy base material is suppressed, and the recess between the Si crystal grains functions as an oil reservoir. Thereby, it is possible to suppress the drag.

In order to more effectively suppress the occurrence of the drag near the top dead center, the inventors of the present invention have made an effort to obtain the following findings.

In a cylinder body made of an Al alloy which is relatively high in Si and manufactured by high pressure die casting, the primary Si crystal grains have an appropriate size from the viewpoint of bearing the load of the piston portion. Properly distributed on the sliding surface. Therefore, if the uniformity of the oil film formed on the sliding surface is improved by uniformly maintaining a sufficient amount of lubricating oil between the primary Si grains in the vicinity of the top dead center, even if the Al alloy base material is in contact with the piston portion, It is also not easy to cause drag. That is, the Al alloy base material can be allowed to come into contact with the piston portion. Moreover, the advantage brought about by the improvement of the uniformity of the oil film can be enjoyed, so that the occurrence of the drag near the top dead center can be more effectively suppressed.

The present invention has been made based on the above findings, that is, contrary to the previous design ideas. Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<engine>

Fig. 1 is a cross-sectional view schematically showing an engine 150 according to an embodiment of the present invention. In the present embodiment, R is a direction in which the piston portion 122 reciprocates. The U system indicates the upward direction, that is, the direction from the cylinder block 100 toward the cylinder head 130. L indicates the downward direction, that is, the direction from the cylinder block 100 toward the crankcase 110. In the following description, a water-cooled engine will be described as an example. However, the present invention is not limited thereto, and may be an air-cooled engine. The engine of this embodiment is a single-cylinder engine. However, in the present invention, the number of cylinders of the engine is not particularly limited. The engine of this embodiment is a four-stroke engine, but it can also be a two-stroke engine.

The engine 150 has a crankcase 110, a cylinder block 100, and a cylinder head 130. In the present embodiment, the cylinder block portion 100 is separated from the crank case 110. However, in the present invention, the cylinder block portion 100 and the crank case 110 may be integrated.

A crankshaft 111 is housed in the crankcase 110. The crank shaft 111 has a crank pin 112 and a crank arm 113.

A cylinder block 100 is disposed above the crankcase 110. The cylinder block portion 100 includes a cylinder wall 103 and an outer wall 104. The cylinder wall 103 has a substantially cylindrical shape. The cylinder wall 103 is formed to define the cylinder bore 102. The outer wall 104 surrounds the cylinder wall 103 and constitutes the outer contour of the cylinder block 100. A water jacket 105 is disposed between the cylinder wall 103 and the outer wall 104.

A piston portion 122 is inserted into the cylinder bore 102 of the cylinder block portion 100. Piston portion 122 The cylinder hole 102 is slid in contact with the sliding surface 101 of the cylinder block 100 (see FIG. 2). The piston portion 122 is formed of, for example, an Al alloy (typically an Al alloy containing Si). The piston portion 122 is formed by forging as disclosed in the specification of U.S. Patent No. 6,205,836. Further, the method of manufacturing the piston portion 122 is not particularly limited. The piston portion 122 can also be formed by, for example, casting.

A cylinder sleeve is not provided in the cylinder bore 102. The inner surface of the cylinder wall 103 of the cylinder block 100 is not plated. In the present embodiment, the cylinder sleeve is not required, so that the manufacturing steps of the engine 150 can be simplified, the weight of the engine 150 can be reduced, and the cooling performance can be improved. Further, since it is not necessary to plate the inner surface of the cylinder wall 103, it is also possible to reduce the manufacturing cost. The present invention is not limited to the embodiment, and for example, a cylinder sleeve may be provided in the cylinder bore 102, and the cylinder sleeve may include the cylinder block portion 100 of the present embodiment. The method of installing the cylinder sleeve is not particularly limited, and examples thereof include embedding into the cylinder bore 102, insert molding, and the like. In this case, the cylinder sleeve has the sliding surface 101 of this embodiment. Further, plating is not performed on the inner surface of the cylinder block portion 100 provided in the cylinder sleeve.

A cylinder head 130 is disposed above the cylinder block 100. The cylinder head 130 forms a combustion chamber 131 together with the piston portion 122 of the cylinder block 100. The cylinder head 130 has an intake port 132 and an exhaust port 133. An intake valve 134 for supplying a mixed gas to the combustion chamber 131 is provided in the intake port 132, and an exhaust valve 135 for exhausting the inside of the combustion chamber 131 is provided in the exhaust port 133.

The piston portion 122 and the crank shaft 111 are coupled by a link 140. Specifically, the piston pin 123 of the piston portion 122 is inserted into the through hole of the small end portion 142 of the link 140, and the crank pin 112 of the crank shaft 111 is inserted into the through hole of the large end portion 144, whereby the piston is inserted The portion 122 is coupled to the crank shaft 111. A roller bearing (rolling bearing) 114 is provided between the inner circumferential surface of the through hole of the large end portion 144 and the crank pin 112. Further, the engine 150 does not have an oil pump for forcibly supplying lubricating oil, but the engine of the present invention may be provided with an oil pump.

2 is a view schematically showing the side of the piston portion 122 of the engine 150 shown in FIG. view.

The piston portion 122 is disposed within the cylinder bore 102. The piston portion 122 includes a piston main body 122a and a piston ring portion 122b. The piston body 122a has a piston pin 123 that is inserted into a through hole of the link 140. The piston ring portion 122b includes three (plurality) piston rings 122c, 122d, and 122e provided on the outer circumference of the piston body 122a.

The piston ring 122c is also referred to as a top ring and is embedded in a top ring groove 122f provided on the outer circumference of the piston body 122a. The piston ring 122d is also referred to as a second ring and is embedded in a second ring groove 122g provided on the outer circumference of the piston body 122a. The piston ring 122e is also referred to as an oil ring and is embedded in an oil ring groove 122h provided on the outer circumference of the piston body 122a. The top ring 122c, the second ring 122d, and the oil ring 122e are spaced apart from each other in the reciprocating direction R of the piston portion 122, and are sequentially disposed from the top to the bottom. That is, in the present embodiment, the upper end 122m of the piston ring portion 122b in the reciprocating direction R of the piston portion 122 corresponds to the upper surface of the top ring 122c. The lower end 122n of the piston ring portion 122b corresponds to the lower surface of the oil ring 122e. In particular, the piston ring portion 122b (piston rings 122c, 122d, 122e) of the piston portion 122 is in contact with the sliding surface 101 of the cylinder wall 103. Further, in the present embodiment, the piston ring portion 122b includes three piston rings, but the number of the piston rings constituting the piston ring portion 122b is not particularly limited.

FIG. 3 is a perspective view schematically showing a cylinder block 100 provided in the engine 150 shown in FIG. 1 . Fig. 4 is a cross-sectional view schematically showing the cylinder block portion 100 shown in Fig. 3.

The cylinder block portion 100 has a sliding surface 101 and is formed of an Al alloy containing Si. Specifically, it is formed of an Al alloy having a Si content of 16% by mass or more. The Al alloy preferably contains 73.4% by mass or more and 79.6% by mass or less of Al, 16% by mass or more and 24% by mass or less of Si, and 2.0% by mass or more and 5.0% by mass or less of copper. The wear resistance and strength of the cylinder block 100 can be improved. Further, the Si content is also preferably 18% by mass or more. The Si content is also preferably 22% by mass or less. The Al alloy preferably contains 50 ppm by mass or more and 200 ppm by mass or less of phosphorus, and 0.01% by mass or less of calcium. When the Al alloy contains 50 ppm by mass or more and 200 ppm by mass or less of phosphorus, coarsening of Si crystal grains can be suppressed, so that Si crystal grains can be uniformly formed. Dispersed in the alloy. In addition, by setting the calcium content of the Al alloy to 0.01% by mass or less, the effect of refining the Si crystal grains of phosphorus can be secured, and a metal structure excellent in abrasion resistance can be obtained.

As shown in FIGS. 3 and 4, the cylinder block portion 100 includes a cylinder wall 103 formed with a sliding surface 101, and an outer wall 104 having a surface exposed on the outer circumference. A water jacket 105 is disposed between the cylinder wall 103 and the outer wall 104. The water jacket 105 is constructed to hold the coolant.

The cylinder block portion 100 includes a sliding surface 101 to which the piston portion 122 (see FIG. 1) is in contact. The sliding surface 101 is a surface (i.e., an inner peripheral surface) of the cylinder bore 103 side of the cylinder wall 103. In other words, the sliding surface 101 is the innermost surface of the inner circumferential surface of the cylinder wall 103 located in the radial direction of the cylinder block 100. Further, in the present invention, the sliding surface 101 is in contact with the piston portion 122, and the sliding surface 101 is in contact with the piston portion 122 via an oil film formed of lubricating oil.

In the present specification, the "upper side" of the sliding surface 101 means the cylinder head side (that is, the top dead center side). The "lower side" of the sliding surface 101 means the crankcase side (that is, the bottom dead center side). The region 101a which is 1/4 of the upper side of the sliding surface 101 means that the entire sliding surface 101 is equally divided into four portions along the sliding direction of the piston (the central axis direction of the cylinder bore 102), and is located at the most cylinder side. region. The area 1/4 of the lower side of the sliding surface 101 is referred to as the area located closest to the crankcase side.

In the present embodiment, the following linear grooves 8 are formed on the entire sliding surface 101 (see Fig. 5). However, the invention is not limited to this example. In the present invention, the portion where the linear groove 8 is formed may be at least the region 101a of the upper side of the sliding surface 101. The portion in which the linear groove 8 is formed may be only the region 101a of the upper side of the sliding surface 101, or the region 101a of the upper side of the sliding surface 101 and the region 101b of the lower side 1/4.

Fig. 5 is a plan view showing an enlarged view of a sliding surface of the cylinder block 100 shown in Fig. 3 in a schematic manner. R is a direction in which the piston portion 122 reciprocates. 6(a) and 6(b) are cross-sectional views showing the sliding surface of the cylinder block 100 shown in Fig. 3 in an enlarged manner and schematically shown. Figure 6 is a cross-sectional view along direction R. In FIGS. 6(a) and 6(b), for the sake of convenience, only the first of the linear grooves 8 is shown. A linear groove 8a.

On the sliding surface 101, a plurality of primary Si crystal grains 1, a plurality of eutectic Si crystal grains 2, and an Al alloy base material 3 are exposed. When the molten metal of the Al-Si-based alloy having a hypereutectic composition is cooled, the Si crystal grains which are initially precipitated are referred to as "primary Si crystal grains". The Si grains deposited next are referred to as "eutectic Si grains". The primary Si crystal grains 1 are relatively large, for example, have a granular shape. The eutectic Si grains 2 are relatively small, for example, have a needle shape. It is not necessary for all the eutectic Si grains 2 to have a needle shape. It is also possible that a part of the eutectic Si grains 2 have a granular shape. In this case, the acicular eutectic Si grains 2 in the plurality of eutectic Si grains 2 are the main crystal grains. The Al alloy base material 3 is a matrix containing a solid solution of Al. The cylinder block portion 100 has a plurality of primary Si crystal grains 1, a plurality of eutectic Si crystal grains 2, and an Al alloy base material 3. A plurality of primary Si crystal grains 1 and a plurality of eutectic Si crystal grains 2 are dispersedly present in the Al alloy base material 3.

The average crystal grain size of the primary Si crystal grains 1 is, for example, 8 μm or more and 50 μm or less. Therefore, a sufficient number of primary Si grains 1 exist per unit area of the sliding surface 101. Therefore, the load applied to each of the primary Si grains 1 during operation of the engine 150 is relatively small. The destruction of the primary Si crystal 1 during operation of the engine 150 can be suppressed. Further, since the portion of the primary Si crystal grains 1 buried in the Al alloy base material 3 is sufficiently large, the fall of the primary Si crystal grains 1 can be reduced. Therefore, the abrasion of the sliding surface 101 due to the falling primary Si crystal grains 1 can also be suppressed. On the other hand, when the average crystal grain size of the primary Si crystal grains 1 is less than 8 μm, the portion of the primary Si crystal grains 1 buried in the Al alloy base material 3 is small. Therefore, when the engine 150 is operated, the falling of the primary Si crystal grains 1 easily occurs. Since the primary crystal Si crystals which have fallen off function as polishing particles, the sliding surface 101 is largely worn. Further, when the average crystal grain size of the primary Si crystal grains 1 exceeds 50 μm, the number of primary Si crystal grains 1 per unit area of the sliding surface 101 is small. Therefore, there is a case where a large load is applied to each of the primary Si crystal grains 1 while the engine 150 is in operation, and the primary Si crystal grains 1 are broken. The fragment of the primary crystal Si crystal 1 that has been destroyed functions as polishing particles, so that the sliding surface 101 is largely worn. Further, the average crystal grain size of the primary Si crystal grains 1 is preferably 12 μm or more.

In the present embodiment, the cylinder block portion 100 is formed of an Al alloy having a Si content of 16% by mass or more by high pressure die casting (HPDC). The high pressure die casting is a casting method in which a molten metal is supplied to a mold at a pressure exceeding atmospheric pressure by applying pressure to the molten metal. By high pressure die casting, a relatively rapid cooling rate (for example, 4 ° C / sec or more and 50 ° C / sec or less) will be partially cooled by the sliding surface 101. Thereby, for example, the average crystal grain size of the primary Si crystal grains 1 can be controlled to be 8 μm or more and 50 μm or less.

The average crystal grain size of the eutectic Si grains 2 is smaller than the average crystal grain size of the primary Si grains 1. The average crystal grain size of the eutectic Si crystal grains 2 is preferably 7.5 μm or less. The eutectic Si crystal 2 functions to reinforce the Al alloy base material 3. Therefore, by making the eutectic Si crystal 2 fine, the wear resistance and strength of the cylinder block 100 can be improved.

Here, the particle size distribution of the Si crystal grains in the cylinder block portion 100 will be described.

Fig. 7 is a graph showing an example of a preferable particle size distribution of Si crystal grains.

In the graph shown in FIG. 7, Si crystal grains having a crystal grain size in the range of 1 μm or more and 7.5 μm or less are eutectic Si crystal grains 2, and Si crystal grains having a crystal grain size of 8 μm or more and 50 μm or less are included. It is a primary Si grain 1. As described above, the Si crystal grains 1 and 2 of the cylinder block portion 100 preferably have a particle size distribution in which the crystal grain size is in the range of 1 μm or more and 7.5 μm or less and the crystal grain size is in the range of 8 μm or more and 50 μm or less. There are peaks respectively. The wear resistance and strength of the cylinder block 100 can be increased to a large extent.

Further, from the viewpoint of reinforcing the Al alloy base material 3 by the eutectic Si crystal grains 2, as shown in Fig. 7, it is preferable that the crystal grain size is in the range of 1 μm or more and 7.5 μm or less (source). The degree at the peak of the eutectic Si crystal grain 2 is 5 times or more the degree of the second peak (from the peak of the primary Si crystal grain 1) in the range of the crystal grain size of 8 μm or more and 50 μm or less.

In order to control the average crystal grain size of the primary Si crystal grains 1 and the eutectic Si crystal grains 2, the cooling rate of the portion to be the sliding surface 101 may be adjusted in the step of casting the molded body (step S1c described below). As a specific example, for example, by using a portion that will become the sliding surface 101 Casting is performed by cooling at a cooling rate of ° C / sec or more and 50 ° C / sec or less, and the average crystal grain size of the primary Si crystal grains 1 may be 8 μm or more and 50 μm or less, and the average crystal grain of the eutectic Si crystal grains 2 The Si crystal grains 1 and 2 were precipitated so that the diameter was 7.5 μm or less.

Next, the linear groove 8 formed on the sliding surface 101 will be described.

As shown in FIGS. 5 and 6 (a) and (b), a plurality of linear grooves 8 are formed in the sliding surface 101. In the present embodiment, the plurality of linear grooves 8 include a plurality of first linear grooves 8a and a plurality of second linear grooves 8b. The plurality of first linear grooves 8a have a shape extending in a direction from the upper left toward the lower right in FIG. 5, and are substantially parallel to each other. The plurality of first linear grooves 8a are formed in a stripe pattern on the sliding surface 101. The plurality of second linear grooves 8b have shapes extending in the direction from the upper right toward the lower left in Fig. 5, and are substantially parallel to each other. The plurality of second linear grooves 8b are formed in a stripe pattern on the sliding surface 101. The plurality of first linear grooves 8a and the plurality of second linear grooves 8b are not parallel to each other but intersect. Thereby, the plurality of linear grooves 8 are formed in a lattice pattern on the sliding surface 101. Further, in FIG. 5, the portion in which the primary Si crystal 1 and/or the eutectic Si crystal 2 and the linear groove 8 are repeated represents a linear groove 8 to pass through the primary Si crystal 1 and/or eutectic. A portion formed by the surface of the Si crystal 2 exposed. At least a portion of the portion is formed with a fractured surface 5a as shown in Fig. 6(b).

At least two or more linear grooves 8 of the plurality of linear grooves 8 are substantially parallel to each other. One of the plurality of linear grooves 8 may be crossed by a portion of the linear grooves 8 (the first linear grooves 8a) and the remaining linear grooves 8 (the second linear grooves 8b). It is also possible that all of the plurality of linear grooves 8 are formed so as not to intersect each other, and are substantially parallel. By "substantially parallel" is meant that adjacent linear grooves 8 extend in a non-intersecting manner. That is, the meaning of "substantially parallel", for example, even if the linear grooves 8 are not strictly parallel due to errors or deviations in the formation of the linear grooves 8, it can also be interpreted as phase in the present invention. The adjacent linear grooves 8 are substantially parallel. Further, the sliding surface 101 has a group of the first linear grooves 8a and the second linear grooves 8b as a group of mutually parallel linear grooves, but in the present invention, the number of the linear grooves which are parallel to each other is There is no special limit. The slots belonging to different groups cross each other. a plurality of linear grooves 8 formed on the sliding surface 101 The pattern formed is not limited to the square lattice pattern as shown in FIG. The pattern formed by the plurality of linear grooves 8 may be a stripe pattern formed by the first linear groove 8a or the second linear groove 8b, or may be a polygonal lattice pattern such as a triangular lattice pattern. An example of a square lattice pattern is a polygonal lattice pattern. Furthermore, the spacing between the grooves of the stripe pattern and the lattice pattern does not have to be fixed.

In the present embodiment, the plurality of linear grooves 8 are formed in a regular pattern (a stripe pattern or a polygonal lattice pattern). In the present embodiment, the Al alloy base material 3 is exposed to the sliding surface 101 together with the primary ring Si crystal 1 in contact with the piston ring portion 122b (the piston portion 122) in the regular pattern. The sliding surface 101 formed with the linear grooves 8 formed into a regular pattern is more uniform than the conventional irregular sliding surface (the sliding surface in which the Si crystal grains are exposed in the floating island shape), thereby further improving the uniformity of dispersion of the lubricating oil. As a result, in the present embodiment, the uniformity of the oil film formed on the sliding surface 101 is high. In addition, in the following, except for the case where the first linear groove 8a and the second linear groove 8b are distinguished, the description about the linear groove 8 is also about the first linear groove 8a and the second linear groove 8b. The description of both.

As shown in FIG. 5, the planar shape of the linear groove 8 has a linear shape in plan view. However, in the present invention, the planar shape of the linear groove 8 is not limited to a linear shape as long as it has a linear shape that does not extend so as to intersect the linear grooves 8 that are substantially parallel to each other. That is, the linear groove 8 may also have a curved shape. The linear groove 8 may have a curved portion and a linear portion. Further, the linear groove 8 may have a curved portion. Further, the planar shape of the plurality of linear grooves 8 may be different depending on the linear grooves 8. It is also possible that all of the linear grooves 8 have the same or substantially the same shape in plan view. Further, each of the plurality of linear grooves 8 does not have to be formed so that the entire area of the sliding surface 101 is continuous. Each of the plurality of linear grooves 8 does not have to extend to the end edge of the sliding surface 101. Each of the plurality of linear grooves 8 may have a portion interrupted on the sliding surface 101.

Regarding the width of the linear groove 8, the width of the linear groove 8 is not particularly limited. The width of the linear groove 8 is preferably smaller than the thickness of the piston ring having the smallest thickness among the piston rings 122c, 122d, 122e. degree. Further, the width of the linear groove 8 is preferably equal to or greater than the average crystal grain size of the primary Si crystal grains 1. The width of the linear groove 8 is preferably equal to or greater than the maximum value of the range of the particle diameter of the primary Si crystal grains 1 in the particle size distribution of the cylinder block portion 100. As shown in Fig. 5, the linear groove 8 has a fixed width, but the present invention is not limited to this example. The linear grooves 8 may also have different widths depending on the position. Further, the width of the plurality of linear grooves 8 may be different depending on the linear grooves 8. It is also possible for all of the linear grooves 8 to have the same width or substantially the same width.

Regarding the depth of the linear groove 8, in the present embodiment, the linear groove 8 has 1/1 of the upper limit of the range of the particle diameter of the eutectic Si crystal 2 in the particle size distribution of the Si crystal grains of the cylinder block 100. 3 or more depths. Here, the meaning of the depth of the linear groove 8 will be described. Patent Document 3 discloses a technique for more effectively suppressing the occurrence of drag around the top dead center. In Patent Document 3, the sliding surface is etched, and the Al alloy base material is eluted substantially uniformly in the depth direction over the entire sliding surface except for the region of the Si crystal grains existing in the floating island shape. Therefore, in the technique of Patent Document 3, it is preferable that the etching treatment is performed such that the Si crystal grains are hard to fall off from the sliding surface or fall off, and it is difficult to form deep recesses or grooves. On the other hand, in the present embodiment, since the linear grooves 8 are formed to be wider than the average crystal grain size of the primary Si crystal grains, the Al alloy base material which can be removed is limited. Therefore, a linear groove 8 having a relatively large depth can be formed. Specifically, in the present embodiment, the linear groove 8 has a depth of 1/3 or more of the upper limit of the range of the particle diameter of the needle-shaped eutectic Si crystal 2, and the eutectic can be prevented or suppressed. The detachment of the Si crystal 2 is performed. The primary Si crystal grains 1 have an average crystal grain size larger than the average crystal grain size of the eutectic Si crystal grains 2, and also prevent or suppress the seizure of the primary Si crystal grains 1. Since a plurality of linear grooves having a relatively large depth and substantially parallel are formed on the sliding surface, a large amount of lubricating oil can be maintained, and the uniformity of dispersion of the lubricating oil is improved. Therefore, in the present embodiment, the fall of the Si crystal grains can be prevented or suppressed, and the uniformity of the oil film can be improved. The linear groove 8 preferably has a depth of 2.0 μm or more. Further, the linear groove 8 may have a depth of 40% or more of the upper limit of the range of the particle diameter of the eutectic Si crystal grains 2 in the particle size distribution of the Si crystal grains of the cylinder block portion 100. Moreover, the particle size of the Si crystal grains of the cylinder block 100 may also be included. The depth of the upper limit of the range of the particle diameter of the eutectic Si crystal grain 2 in the cloth is 1/2 or more.

Further, the linear grooves 8 preferably have a depth smaller than the upper limit of the range of the particle diameter of the eutectic Si crystal grains 2. This is because the lubricating oil held in the linear groove 8 can be supplied to the sliding surface 101 appropriately and efficiently. Further, the linear groove 8 preferably has a depth of 6.0 μm or less. Further, in the present invention, when the depth limit value and the lower limit value of the linear groove 8 are defined, a groove having a depth smaller than the depth lower limit of the linear groove 8 may be formed on the sliding surface 101. And/or a groove having a depth greater than a limit above the depth of the linear groove 8. In other words, in the present invention, grooves other than the linear grooves defined in the present invention may be formed on the sliding surface.

The cross-sectional shape of the linear groove 8 is a shape in which the width of the linear groove 8 becomes smaller as the depth of the linear groove 8 becomes larger. The cross-sectional shape of the linear groove 8 is a sectional shape of the linear groove 8 on a plane perpendicular to the direction in which the linear groove 8 extends. Further, in the present invention, the cross-sectional shape of the linear groove 8 is not particularly limited. The cross-sectional shape of the linear groove 8 may be, for example, a substantially V shape as shown in Fig. 6(a) or a substantially U shape. Further, the cross-sectional shapes of the linear grooves 8 need not be the same. The cross-sectional shape of the linear groove 8 may vary depending on the position, or may vary depending on the linear groove 8. Further, the portion (mountain) between the linear grooves 8 is not necessarily a flat surface as shown in Figs. 5 and 6 (a) and (b). The portion between the linear grooves 8 may be an inclined surface or a ridge line, or may form one or a plurality of grooves having a depth smaller than that of the linear grooves 8.

Regarding the distance between the first linear grooves 8, a plurality of substantially linear first grooves 8a are formed to be wider than the average crystal grain size of the primary Si crystal grains 1. As a result, at least a part of the plurality of primary Si crystal grains 1 is located between the first linear grooves 8a adjacent to each other. In the present embodiment, both the primary Si crystal grains 1 and the Al alloy base material 3 are exposed to the sliding surface 101 in contact with the piston portion 122 in the region between the adjacent first linear grooves 8a. The portion of the sliding surface 101 that is in contact with the piston portion 122 is adjacent to the first linear groove 8a in a plan view, so that the supply of the lubricating oil to the sliding surface 101 can be smoothly performed. Further, the Al alloy base material 3 is exposed to the sliding surface 101 so as to be in contact with the piston portion 122, and the primary Si crystal grains 1 are also exposed to the sliding surface 101 so as to be in contact with the piston portion 122, so that the sliding can be more effectively suppressed. Face 101 (Al combined Gold base metal 3) wear. In Fig. 5, the distance between one of the adjacent pairs of the first linear grooves 8a is fixed regardless of the position, but the present invention is not limited to this example. That is, the distance between one of the adjacent pairs of the first linear grooves 8a does not have to be fixed. For example, the first linear grooves 8a adjacent to each other are formed in a meandering manner, and the distance between the first linear grooves 8a may be different depending on the position. Incidentally, the above description has been made regarding the first linear groove 8a, but the description of the second linear groove 8b is the same as that of the first linear groove 8a, and thus the description thereof is omitted.

In the present embodiment, as shown in FIG. 5, at least one of the linear grooves 8 is formed by passing the primary Si crystal grains 1 by breaking the primary Si crystal grains 1. That is, at least one of the linear grooves 8 is formed to pass through the exposed surface of the primary Si crystal grains 1. Thereby, the uniformity of dispersion of the lubricating oil of the sliding surface 101 can be further improved. The invention is not limited to this example.

In the present embodiment, as shown in FIG. 6(b), the primary Si crystal grains 1 having the fractured surface 5a are exposed on the sliding surface 101. That is, in the present embodiment, at least a part of the primary Si crystal grains 1 exposed on the sliding surface 101 is broken, and is destroyed, so that the surface formed on the primary Si crystal grains 1 (that is, the fractured surface 5a) is exposed. Sliding surface 101. Thereby, the oil reservoir portion 5b is formed on the sliding surface 101. Since the fractured section of the primary Si crystal 1 has irregularities, the amount of lubricating oil that can be maintained by the oil reservoir 5b is large. The opening area of the oil reservoir portion 5b is the same as the cross-sectional area of the primary Si crystal grain 1 (the area exposed by the sliding surface 101). The depth of the oil reservoir 5b is smaller than the diameter of the primary Si crystal 1. The oil reservoir 5b including the fractured portion 5a of the primary Si crystal 1 is formed on the sliding surface 101 together with a plurality of substantially linear first grooves 8a. Therefore, the amount of the lubricating oil can be increased while maintaining the uniformity of the dispersion of the lubricating oil. It can suppress the grinding more effectively. The broken section 5a is formed when the surface processing of the cylinder block 100 is performed after casting of the cylinder block 100. Specifically, the fractured section 5a is formed, for example, when the primary Si crystal grains 1 are ground by a grindstone.

In the present embodiment, the cylinder block portion 100 is formed of an Al alloy having a Si content of 16% by mass or more. The level of the primary Si crystal 1 exposed in the region 101a of the upper side 1/4 of the sliding surface 101 The average crystal grain size is 8 μm or more and 50 μm or less. From the viewpoint of bearing the load of the piston portion 122, the primary Si crystal grains 1 have an appropriate size and are appropriately distributed on the sliding surface. Under this condition, the primary Si crystal grains 1 and the Al alloy base material 3 are exposed in contact with the piston portion 122, and have particles of the eutectic Si crystal grains 2 in the particle size distribution of the Si crystal grains of the cylinder block portion 100. The plurality of substantially linear grooves 8 (the first linear grooves 8a and the second linear grooves 8b) having a depth equal to or greater than 1/3 of the upper limit of the diameter range are wider than the primary Si grains 1 The average crystal grain size is formed between the distances. The uniformity of dispersion of the lubricating oil of the sliding surface 101 can be improved by forming a plurality of substantially linear grooves 8 which are wider than the average crystal grain size of the primary Si crystal grains 1. Thereby, the uniformity of the oil film formed on the sliding surface can be improved. Further, the plurality of linear grooves 8 have a depth of 1/3 or more of the upper limit of the range of the particle diameter of the eutectic Si crystal grains 2 in the grain size distribution of the Si crystal grains of the cylinder block portion 100, so that a sufficient amount can be obtained. The lubricating oil is held in the linear groove 8. Therefore, the oil film crack on the sliding surface can be suppressed. Further, a plurality of linear grooves 8 have portions passing between the primary Si crystal grains 1 adjacent to each other. Thereby, since the primary crystal Si crystal 1 receives the load of the piston portion 122, abrasion of the sliding surface 101 (Al alloy base material 3) adjacent to both sides of the linear groove 8 can be suppressed, and the linear groove 8 can be easily held. Lubricating oil inside.

The Al alloy base material 3 is exposed to the sliding surface 101 so as to be in contact with the piston portion 122. In the past, it has been considered that the contact of the Al alloy base material 3 with the piston portion 122 is unsatisfactory from the viewpoint of suppressing the drag. However, in the present embodiment, the Al alloy base material 3 is exposed to the sliding surface 101 together with the primary Si crystal grains 1 having an appropriate size and appropriately distributed on the sliding surface 101. Further, as described above, the uniformity of the oil film formed on the sliding surface 101 can be improved, and a sufficient amount of lubricating oil can be maintained. Therefore, the influence of the contact between the Al alloy base material 3 and the piston portion 122 can be suppressed to an acceptable level, and the effect of suppressing the drag caused by the improvement of the uniformity of the oil film can be obtained. As a result, the occurrence of the drag can be more effectively suppressed.

<Manufacturing method>

A method of manufacturing the cylinder block 100 in the present embodiment will be described.

The cylinder block portion 100 is manufactured, for example, by sequentially performing the following steps S1 to S4.

Step S1 Preparing a shaped body

Step S2 Precision boring

Step S3 rough grinding

Step S4, finally pondering

In the method of manufacturing the cylinder block 100, first, a molded body formed of an Al alloy containing Si is prepared (step S1). The formed body contains primary Si crystal grains and eutectic Si crystal grains in the vicinity of the surface. The step S1 of preparing the molded body includes, for example, steps S1a to S1e.

Step S1a Preparation of Al alloy containing niobium

Step S1b produces a melt

Step S1c High Pressure Die Casting

Step S1d heat treatment

Step S1e Machining

First, an Al alloy containing Si is prepared (step S1a). In order to sufficiently improve the wear resistance and strength of the cylinder block 100, it is preferable to use 73.4% by mass or more and 79.6% by mass or less of Al, 16% by mass or more and 24% by mass or less of Si, and 2.0% by mass or more. And an Al alloy of copper of 5.0% by mass or less is used as an Al alloy.

Next, the prepared Al alloy is heated and melted by a melting furnace to form a molten metal (step S1b). Preferably, about 100 ppm by mass of phosphorus is added in advance to the Al alloy or the melt before the melting. When the Al alloy contains 50 ppm by mass or more and 200 ppm by mass or less of phosphorus, the Si crystal grains can be suppressed from being coarsened, so that Si crystal grains can be uniformly dispersed in the alloy. In addition, by setting the calcium content of the Al alloy to 0.01% by mass or less, the effect of refining the Si crystal grains by phosphorus can be secured, and a metal structure excellent in abrasion resistance can be obtained. That is, the Al alloy preferably contains 50 ppm by mass or more and 200 ppm by mass or less of phosphorus, and 0.01% by mass or less of calcium.

Then, casting is performed by high pressure die casting using a molten alloy of an Al alloy (step S1c). That is, the melt is cooled in a mold to form a molded body. At this time, by the cylinder wall The portion of the sliding surface 101 that is 103 is cooled at a relatively fast cooling rate (for example, 4 ° C / sec or more and 50 ° C / sec or less), and is obtained in the vicinity of the surface to have a Si grain which contributes to wear resistance. Shaped body. This casting step S1c can be carried out using, for example, a casting apparatus disclosed in the specification of International Publication No. 2004/002658.

Next, any of the heat treatments called "T5", "T6", and "T7" is performed on the molded body taken out from the mold (step S1d). The T5 treatment is a treatment in which the formed body is quenched by water cooling or the like immediately after being taken out from the mold, and then, in order to achieve improvement in mechanical properties or dimensional stabilization, artificial aging is performed at a specific temperature for a specific time, and thereafter, gas is produced. cold. The T6 treatment is a treatment in which the shaped body is subjected to a solution treatment at a specific temperature for a specific time after being taken out from the mold, followed by water cooling, and then subjected to artificial aging treatment at a specific temperature for a specific period of time, followed by air cooling. The T7 treatment system is over-aged compared to the T6 treatment, and although the size stabilization can be achieved more than the T6 treatment, the hardness is lower than the T6 treatment.

Then, the molded body is subjected to specific machining (step S1e). Specifically, grinding is performed on the joint surface with the cylinder head or the joint surface with the crankcase.

After preparing the molded body as described above, precision boring processing for adjusting the dimensional accuracy is performed on the surface of the molded body, specifically, the inner peripheral surface of the cylinder wall 103 (that is, the surface on which the sliding surface 101 is formed) (step S2) .

Next, the surface subjected to the precision boring processing is subjected to rough honing treatment (step S3). That is, the surface to be the sliding surface 101 is polished using a grindstone having a small number of grits (a grindstone having a large abrasive grain). In the present embodiment, the entire region of the surface of the molded body which is the surface of the sliding surface 101 is subjected to rough honing treatment, but the present invention is not limited to this example. In the present invention, it is only necessary to perform a rough honing process on at least a quarter of the upper side of the sliding surface 101.

Then, final honing processing is performed (step S4). That is, a grindstone having a relatively large particle size number (grinding stone having a small abrasive grain) is used as an area of the surface of the formed body which becomes the sliding surface 101. Grinding. Further, the rough honing treatment and the final honing treatment can be carried out using, for example, a honing device as disclosed in Japanese Laid-Open Patent Publication No. 2004-268179. Further, the specifications of the grindstone in the rough honing treatment and the final honing treatment (the type of the abrasive grains, the number of the crystal grains (the grinding particle diameter), the type of the bonding agent, and the like) may be based on the linear grooves 8 formed on the sliding surface 101. Set according to the specifications.

Through the above steps, the sliding surface 101 of the present embodiment is formed. On the sliding surface 101, a plurality of primary Si crystal grains 1 and an Al alloy base material 3 are exposed. When the piston portion 122 reciprocates in the cylinder bore 102, the plurality of primary Si crystal grains 1 and the Al alloy base material 3 come into contact with the piston portion 122. Further, the sliding surface 101 has a plurality of linear grooves 8 at least in a region of 1/4 of the upper side of the sliding surface 101. The plurality of linear grooves 8 include a plurality of first linear grooves 8a substantially parallel to each other, and a plurality of second linear grooves 8b substantially parallel to each other. In the present embodiment, the linear groove 8 is formed by the grindstone, but the present invention is not limited to this example. The linear groove 8 can also be formed by, for example, a laser. Further, the number of times of the rough honing treatment and the final honing treatment is not limited to one, and may be two or more.

<cylinder block member>

The cylinder block member in the present embodiment is the cylinder block portion 100 itself (see Fig. 1 and the like). The cylinder block 100 has a portion of the sliding surface 101. However, in the present invention, the cylinder block member is not limited to this example. The cylinder block member may be provided with the cylinder block portion 100 having the sliding surface 101. The cylinder block member in the present invention may be a member (so-called cylinder) formed by integrally molding the cylinder block 100 and the crank case 110. The cylinder block member of the present invention may also be a cylinder sleeve that is used by being disposed in the cylinder bore 102. Since the cylinder block member has the sliding surface 101 described above, the application of the engine can more effectively suppress the occurrence of the drag of the engine (especially near the top dead center).

<vehicle>

The vehicle of the present invention includes various types of vehicles such as snowmobiles such as automobiles, locomotives, and snowmobiles, and the number of wheels is not particularly limited, and is four wheels, three wheels, and two wheels. Again, this The vehicle of the invention may be a box type vehicle in which an engine is disposed in a portion away from the seat such as an engine room, and a straddle type vehicle in which at least a part of the engine is disposed below the seat portion and the driver rides over the seat portion. The straddle-type vehicle also includes a vehicle that can be used by the driver to ride the knees together.

Hereinafter, a locomotive will be described as an example of a vehicle.

Fig. 8 is a side view schematically showing a locomotive having the engine 150 shown in Fig. 1.

In the locomotive shown in FIG. 8, a head pipe 302 is provided at the front end of the body frame 301. In the head pipe 302, a front fork 303 is attached so as to be rockable in the left-right direction of the vehicle. At the lower end of the front fork 303, the front wheel 304 is rotatably supported. At the upper end of the front fork 303, a handle 305 is provided.

The rear frame 306 is attached in such a manner as to extend rearward from the upper end portion of the rear end of the body frame 301. A fuel tank 307 is disposed on the body frame 301, and a main seat portion 308a and a tandem seat 308b are disposed on the rear frame 306.

Further, at the rear end of the body frame 301, an arm 309 extending rearward is attached. The rear wheel 310 is rotatably supported at the rear end of the rear arm 309.

At the central portion of the body frame 301, the engine 150 shown in Fig. 1 is held. In the engine 150, the cylinder block portion 100 in the present embodiment is used. A radiator 311 is provided in front of the engine 150. An exhaust pipe 312 is connected to the exhaust port of the engine 150, and a muffler 313 is attached to the rear end of the exhaust pipe 312.

A transmission 315 is coupled to the engine 150. A drive sprocket 317 is mounted to the output shaft 316 of the transmission 315. The drive sprocket 317 is coupled to the rear wheel 310 and the wheel sprocket 319 via a chain 318. The transmission 315 and the chain 318 function as a transmission mechanism that transmits power generated by the engine 150 to the drive wheels.

In the locomotive (vehicle) according to the present embodiment, the engine 150 including the cylinder block portion 100 having the sliding surface 101 is mounted, so that the occurrence of the drag near the top dead center can be more effectively suppressed.

The measurement of the average crystal grain size of the primary Si crystal grains and the eutectic Si crystal grains is performed by image processing using a portion of the cylinder body portion which is a sliding surface. Based on the area of the Si crystal grains in the image obtained by the image processing, the diameter (equivalent diameter) of each Si crystal grain in the case where the Si crystal grains in the assumed image are in a true circle is calculated. Further, fine crystals having a diameter of less than 1 μm are not counted in Si crystal grains (primary Si crystal grains or eutectic Si crystal grains). From the above, the number (degrees) and diameter of Si crystal grains are specified. Based on this, the particle size distribution of the Si crystal grains in the cylinder body portion is obtained. The particle size distribution is, for example, a histogram as shown in FIG. The particle size distribution contains 2 peaks. The particle size distribution is divided into two regions by setting the diameter of the portion forming the valley between the two peaks to a threshold value. The region corresponding to the larger diameter is set as the particle size distribution of the primary Si grains. The region corresponding to the smaller diameter is the particle size distribution of the eutectic Si grains. Further, the average crystal grain size of the primary Si crystal grains and the average crystal grain size of the eutectic Si crystal grains were calculated based on the respective particle size distributions.

The width of the linear groove refers to the distance between one pair of ridge lines adjacent to each other in a cross section (cross-sectional curve) crossing the linear groove. Further, the cross-section of the piston portion is parallel to the sliding direction of the sliding surface (the reciprocating direction R of the piston portion). Further, the cross section is also parallel to the radial direction of the cylinder block. The depth of the linear grooves is the depth from the higher ridge line of one of the ridge lines adjacent to the linear groove to the deepest portion of the linear groove. The distance between the linear grooves is the distance between one of the adjacent sections (section curves) and the deepest part of the groove. Further, when the sliding surface adjacent to the linear groove is substantially a flat surface, the width of the linear groove is the distance between the edges of the pair of sliding surfaces (flat surfaces).

In the present invention, as the width, depth, and pitch of the linear grooves, the average value of the linear grooves included in the cross-sectional curve of the distance of 3 to 5 mm is used. Further, in the present invention, a groove other than the linear groove having the depth defined in the present invention may be formed on the sliding surface. In this case, a linear groove having a depth defined by the present invention is used in the case of the width and the pitch of the specific linear groove.

The terms and expressions used in this article are used for the purpose of explanation, not for limiting solutions. Released. It is to be understood that the invention is not to be construed as being limited by the scope of the invention.

The present invention has been made in a variety of different forms. The present disclosure should be considered as an embodiment of the principles of the invention. The embodiments are not intended to limit the invention to the preferred embodiments described and/or illustrated herein, and various embodiments are described herein.

Several illustrative embodiments of the invention are described herein. The invention is not limited to the various preferred embodiments described herein. The present invention also includes all embodiments that include equivalent elements, modifications, deletions, combinations (e.g., combinations of features across various embodiments), improvements, and/or changes that can be discerned by the present disclosure. The limitation of the scope of the patent application should be construed broadly based on the terms used in the scope of the patent application, and should not be limited to the embodiments described in the specification or the litigation of the present invention. Such an embodiment should be construed as non-exclusive. For example, in the present disclosure, the term "preferred" is non-exclusive and means "preferably, but not limited to".

1‧‧‧ primary crystal Si grain

2‧‧‧ Eutectic Si grains

3‧‧‧Al alloy base metal

5a‧‧‧ broken section

5b‧‧‧Oil Accumulation Department

8a‧‧‧First linear groove

101‧‧‧Sliding surface

Claims (10)

An engine including a piston portion and a cylinder block having a sliding surface on which the piston portion slides, wherein the cylinder block portion is formed of an Al alloy having a Si content of 16% by mass or more, and includes an average crystal grain. a primary Si crystal having a diameter of 8 μm or more and 50 μm or less, a eutectic Si crystal grain having an average crystal grain size smaller than an average crystal grain size of the primary Si crystal grain, and an Al alloy base material on the sliding surface At least 1/4 of the upper side of the sliding surface, the primary Si crystal grains and the Al alloy base material are exposed in contact with the piston portion, and have a particle size distribution of Si crystal grains of the cylinder block portion a substantially parallel plurality of linear grooves having a depth of 1/3 or more of a range of the above-mentioned eutectic Si crystal grain size, which is formed to be wider than an average crystal grain size of the primary Si grains; There is a portion between the above-mentioned primary Si grains which are adjacent to each other. An engine including a piston portion and a cylinder block having a sliding surface on which the piston portion slides, and the cylinder block portion is formed of an Al alloy having a Si content of 16% by mass or more by high pressure die casting. And a primary crystal Si crystal grain, a eutectic Si crystal grain having an average crystal grain size smaller than an average crystal grain size of the primary crystal Si crystal grain, and an Al alloy base material, wherein at least the sliding surface of the sliding surface a region of 1/4 of the upper side, the primary Si crystal grains and the Al alloy base material being exposed in contact with the piston portion, and having the eutectic Si crystal in the particle size distribution of the Si crystal grains of the cylinder block portion a substantially parallel plurality of linear grooves having a depth greater than 1/3 of the upper limit of the range of the particle diameter is formed to be wider than the average crystal grain size of the primary Si crystal grains, and has an adjacent The portion between the primary Si grains. Such as the engine of claim 1 or 2, wherein The plurality of linear grooves have a thickness limit of 1/3 or more of the range of the eutectic Si crystal grain size in the particle size distribution of the Si crystal grains of the cylinder block portion, and are smaller than the eutectic Si crystal grain size. The depth of the upper limit of the range. The engine according to any one of claims 1 to 3, wherein the plurality of linear grooves have a depth of 2.0 μm or more and 6.0 μm or less. The engine of any one of claims 1 to 4, wherein between the adjacent linear grooves, the primary Si crystal grains and the Al alloy base material are in contact with the piston portion Exposed to the sliding surface described above. The engine of any one of claims 1 to 5, wherein the piston portion includes: a piston body; and a piston ring portion including a plurality of piston rings disposed on an outer circumference of the piston body; the plurality of linear grooves It is formed at a pitch wider than the average crystal grain size of the primary Si crystal grains and smaller than the distance from the lower end of the piston ring portion to the upper end of the piston ring portion in the reciprocating direction of the piston portion. The engine of any one of claims 1 to 6, wherein the piston portion is provided with: a piston body; and a piston ring disposed at an outer circumference of the piston body; the plurality of linear grooves having a thickness smaller than a thickness of the piston ring width. The engine according to any one of claims 1 to 7, wherein at least a part of the primary Si crystal grains exposed on the sliding surface is broken, and the surface formed on the primary Si crystal grains is exposed on the sliding surface due to being broken. A cylinder block member comprising the above-described cylinder block portion included in an engine of any one of claims 1 to 8. A vehicle having the engine of any one of claims 1 to 8.